Nab
a fingerprint image from the computer (go to yahoo.com and
select IMAGES directly above the search bar - then type in
fingerprint and you'll get a nice selection to choose from.)
Copy and paste the image (once you click on it to get the
full size) into a WORD document and enlarge it to fit the
page. These can be then printed out and hung (you could also
cut them out prior to hanging them up.)

Take
a grown man's pair of shoes and trace out the soul (each shoe)
onto a piece of cardboard. Once you cut these out, you'll
have a great stencil for creating numerous footprints to place
throughout your location. They can have multiple purposes
(aside from just looking great spread throughout) including
showing people where to stand in line for food, as part of
game you already have planned or even fun paths to follow
leading to different locations within your party space.

UNDER
SUPERVISION, this is something the kids would LOVE to help
with. Find yourself a stamp pad (they make washable ones for
kids.) Using your own fingers, stamp fingerprints on the balloons,
streamers and whatever other decorations you might be hanging
about your party!

With
standard white chalk, draw an outline of a dead body on the
pavement. This would be a great place to use some of that
yellow CAUTION tape.

Obtain
some photos ahead of time of some of your guests and create
FBI wanted posters (visit your local US post office to see
the style and format.) Have fun coming up with different reasons
why the FBI might be looking for them - knowing the guests,
you could get crazy with it!